Hello!
At macro-expansion time, I need to determine whether a given identifier is
defined. I failed to find any standard PLT facility for this purpose in the
documentation.
I thought of the following solution:
(require (lib "defmacro.ss"))
; Return `body' if `id' is not defined
(define-macro (ifndef id body)
(with-handlers
(((lambda (x) #t)
(lambda (x) `,body)))
(eval id)
#t))
(ifndef
string-upcase
(define (string-upcase str) ...))
It works; however, I do not like calling `eval' in the macro body.
Could you suggest a more elegant solution?
Thank you,
Dmitry